1. Field of the Invention
The present invention relates to a self-cancelling mechanism for cancelling a turn-signal switch of a vehicle put in an actuated condition in response to a steering operation of the vehicle.
2. Description of the Prior Art
A turn-signal switch mounted on a steering column of a vehicle functions to actuate turn-signal lamps, for example right side turn-signal lamps, to signal a change of a running direction of the vehicle to succeeding vehicles and the like by a driver's operation of a turn-signal lever prior to the rotation of a steering wheel of the vehicle.
After this, the driver rotates the steering wheel to the right side to change the running direction of the vehicle. When the change of the running direction is completed, the steering wheel is returned back to its neutral position and by this return action, namely the rotation of the steering wheel in a cancelling direction, a self-cancelling mechanism acts to return the turn-signal switch back to a neutral position so that the turn-signal lamps are switched off.
In such a self-cancelling mechanism, in general, a ratchet is mounted on a bracket rotated by the turn-signal lever and is relatively movable to the bracket in a predetermined distance, and the ratchet is moved into a rotation locus of a cancelling cam which is rotated together with a steering shaft of the vehicle at the time of the rotation of the turn-signal lever so that the turn-signal lever is returned back to the neutral position by the rotation of the steering shaft in a cancelling direction.
In addition, when the steering wheel is rotated in the direction reverse to the cancelling direction with actuated, or blinking, turn-signal lamps the ratchet is relatively moved to the bracket so that the bracket is maintained in its rotation position and the turn-signal lamps are kept in their blinking condition. This relative movement is cancelled when the cancelling cam is separated from the ratchet, and the ratchet is returned back to its original position by a returning force of a return spring. By this returning force the ratchet is caused to strike against the bracket and striking noises occur continuously due to the rotation of the steering wheel in an anti-cancelling direction.
For this reason, for example, U.S. Pat. NO. 4,335,284 has proposed a turn-signal switch in which shock absorbing members are provided between a ratchet and a bracket.
In this switch, however, the shock absorbing members absorb kinetic energy of the ratchet but the ratchet still strikes against the bracket in the same manner as the conventional arts whereby the striking noises occur.